(Or what's the best way to read the books?)
All the books in my world break down in the following ways:
A series embodies a specific location, set of principles or ideas, or even base concepts.
Within each series, there are collections. These contain a full arc of a larger story. While the individual books have a story arc in themselves, they are best read in the numbered order, or through one of the alternative paths.
Every series will crossover in some way to other series. Most often this is through the characters, as they traverse the various paths they choose along their journeys.
Series: Empyrean Club
Collection: The Atlas Collection (series)
Best Reading Order:
Mask Me (Book 1) - Atlas/Reece (Trilogy Story)
Master Me (Book 2) - Jillian/Ian (Side story gives information on timeline) - Complete couple's arc
Reveal Me (Book 3) - Atlas/Reece (Trilogy Story)
Submit to Me (Book 4) - Jessica/Kade (Side story give information on timeline) - - Complete couple's arc
Play with Me (Book 5) - Atlas/Reece (Conclusion of Trilogy)
All Series have Collections and will often crossover to other series/collections.